Inverse Quantity of demand- I feel like an idiot

CFA Level I Economics
#1

I feel like an idiot but can anyone show me how to calculate the Inverse of Demand quantity? I not have a finance undergraduate degree and I can’t figure out what the calculation looks like.

In the Schweser books Pg 13 Book 2 they show and example of Aggregating Consumer Demand.

The demand quantity for gas is:

QDgas= 138500-12500Pgas I understand how to get to this answer but I am having difficulting getting the inverse answer of Pgas=11.08-.00008QDgas

Could someone please show me the calculation so I can figure it out.

Much appreciated. Thanks!

#2

all you have to do is isolate QDgas QD = 138500 - 12500P rearranging: 12500P = 138500 - QD then divide 12500 by both sides p = 11.08 - .00008QD

Bang.

#3

Make Pgas be the subject then divide by 12500 throughout.

Qd(gas)= 138,500 - 12,500 Pgas

Pgas = (138,500/12,500) - [**Qd(gas)/**12,500]

Pgas = 11.08 - 0.00008Qd(gas)

smiley